vgsp-gr r598 diag: peek the ring slots past GP_PUT at the launch decision

The r568 lever is the driver's ring WRITE pointer, not the GPFIFO put:
the b copy entry exists in the ring before the client publishes GP_PUT.
Add a bounded diagnostic (gsp_phys_gr_peek) that, when a channel reads
as drained, dumps up to four slots past last_get with {va,len} and
whether the slot already executed that exact entry - so the next fix can
be grounded in what is actually written ahead of the put.

1 files changed, 4 insertions, 0 deletions

diff --git a/kernel/main.c b/kernel/main.c
index d821762..81bae08 100644
--- a/kernel/main.c
+++ b/kernel/main.c
@@ -2752,6 +2752,10 @@ MODULE_PARM_DESC(sema_copy_dst2, "Second destination window for sema_copy_dst (d
  * the release the client synchronizes on; the translation usually lands within
  * a service pass.
  */
+module_param_named(gsp_phys_gr_peek, gsp_phys_gr_peek, uint, 0644);
+MODULE_PARM_DESC(gsp_phys_gr_peek,
+		 "Peek the ring slots past GP_PUT at each GR launch decision (diagnostic, default 0)");
+
 module_param_named(sema_ce_grace_ms, gsp_sema_ce_grace_ms, uint, 0644);
 MODULE_PARM_DESC(sema_ce_grace_ms, "CE pending-entry grace window in ms (default 25000)");